Nickel-magnesium addition alloy



A ril 17, 1962 K. D. MILLIS 3,030,205

NICKEL-MAGNESIUM ADDITION ALLOY Filed July 20, 1959 O-O7% RETAINED Mg I \JQRETAINED Mg IO 20 3O 4O 5O MAGNESIUM CONTENT IN ALLOY ADDITION REQUIRED TO PRODUCE PREDETERMINED Mg CONTENT 5 KEITH DWIGHT MILLIS INVENTOR.

BY QL. ja M ATTORNEY United States Patent 9 3,030,205 NICKEL-MAGNESIUM ADDITION ALLOY Keith D. Millis, Scotch Plains, N.J., assignor to The International Nickel Company, Inc., New York, N.Y., a

corporation of Delaware Filed July 20, 1959, Ser. No. 828,311 3 Claims. (Cl. 75-130) The present invention relates to an improved method for introducing magnesium into cast iron and, more particularly, to a method for producing magnesium-containing cast iron characterized by improved economy and a high recovery of magnesium into molten iron.

The problem of introducing magnesium into molten cast iron is complicated by the fact that magnesium boils at a temperature below that at which cast iron melts. Many means have been proposed to cope with this problem, including the use of a variety of magnesium alloys, the use of special pressure apparatus to contain the magnesium vapor generated by contact of magnesium with molten cast iron, etc. All of the prior proposals have been characterized by drawbacks such as undesirable violence of addition reactions, expensive and complicated equipment, etc.

An improved method has now been discovered wherein magnesium may readily be introduced into molten cast iron with improved economy, with the use of very simple apparatus and without encountering excessive or explosive addition reactions.

It is an object of the present invention to provide a process for treating cast iron melts to improve the recovery of magnesium in castings produced from such melts.

Another object of the invention is to provide a special magnesium alloy which provides improved recovery of contained magnesium in molten iron treated therewith.

It is a further object of the invention to provide an improved method for introducing magnesium into molten iron which, in cooperation with the special magnesiumcontaining alloy contemplated in accordance with the in vention, provides special and improved results by way of economy and low reactivity.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing which depicts graphically special cooperative effects obtained in carrying out the process embodying the present invention.

Generally speaking, the method embodying the present invention comprises treating a bath of molten cast iron by immersing below the surface thereof a nickel-base alloy containing about 25% to about 32% magnesium, up to about 2% carbon, up to about 5% calcium, up to about 30% silicon, up to about 2% of a rare earth metal, and the balance essentially nickel, holding said alloy be low the surface of said bath until it is substantially melted and dissolved therein, and thereafter casting metal from said bath to obtain magnesium-containing cast iron.

Advantageously, the alloy contains about 1% to about 2% carbon, as the carbon assists in preparing the alloy and reduces the melting point thereof, thereby assisting in control of the addition reaction. Calcium present in the alloy also assists in control of the addition reaction. It is desirable that the magnesium content of the alloy not exceed substantially 35% and that the minimum content of magnesium in the alloy be at least about 25% in order to obtain optimum results by way of high magnesium recovery in the melt, low reactivity of the alloy in contact with molten cast iron, and high economy in the use of nickel. The alloy may also contain silicon in amounts up to about 30% in place of nickel. The nickel content must in all cases be at least about 40% of the alloy. The alloy may advantageously contain a rare earth metal such as cerium or mischmetal in amounts up to about 2% of the alloy, as these elements aid in overcoming the deleterious effects of elements such as titanium, lead, copper, indium, thallium, tin, bismuth and antimony upon the function of magnesium in controlling the occurrence of spheroidal graphite in cast iron.

The apparatus employed for the purpose of immersing the special nickel-magnesium alloy below the molten iron It comprises a: container which may take the form of a cup, can or surface is very simple and inexpensive.

basket which may be made, for example, of sheet metal, graphite, metal-reinforced refractory material, etc. and which may be attached to a rod or pole for immersion into the molten cast iron. Suitable holes maybe provided in the walls of the cup or can and the end thereof which becomes the bottom end upon immersion into the molten iron may advantageously be left open. In using the apparatus, the nickel-magnesium alloy, which may be in the form of small lumps averaging about 5 inch to about 4 inches in diameter, is fitted into the cup or can from the open end. The lumps of alloy may be placed in;

a paper bag and wired or otherwise fastened into the cup or can. The cup or can is then thrust beneath the surface of the melt by means of the attached handle and held in place until subsidence of the addition reaction. Use of a bag made of paper or the like is especially convenient since weighed portions of alloy calculated to be suflicient for treating the weight of molten metal contemplated may be prepared beforehand and inserted into the addition device as required.

It is important that a relatively deep ladle or other: receptacle be employed for the purpose of holding the' molten cast iron melt to be treated in accordance with the invention. It is also important that the addition alloy be thrust Well beneath the melt surface and held in that position until subsidence of the addition reaction. In'

an inch of the bottom of the metal column. In this manner, the alloy melts from the heat of the molten iron and the magnesium contained therein is vaporized. The re-' sulting magnesium vapors are caused to bubble up through the column of molten metal, with the result that the maximum absorption of magnesium in the iron is effected.

The accompanying drawing illustrates the cooperative effects obtained in carrying out the process embodying the present invention. The drawing is based upon the results of a number of tests in accordance with the invention involving the treatment of molten iron at a temperature of about 2700 F., said base iron having a low sulfur content of about 0.03% and wherein the addition alloy was thrust beneath the surface of the molten cast iron to a depth of about 1 inch from the ladle bottom in each case. By

reference to the drawing, it will be seen that the process embodying the present invention makes it possible to employ lower and substantially constant quantities of a special magnesium-containing agent to produce a predetermined magnesium content in cast irons, particularly when the magnesium content in the alloy falls within the range of about 25% to about 32%. It is to be seen from the drawing that when the magnesium content of the agent is either above or below the aforementioned range that greater quantities of addition alloy are required to obtain the predetermined magnesium content in the final Advan-' cast iron. In addition, when the magnesium content of the alloy substantially exceeds about 35%, the addition reaction becomes undesirably violent. The relationship illustrated by the shape of the curve in the accompanying drawing depicts generally cooperative eflects obtained in carrying out the process embodying the present invention although it will be appreciated that the amount of addition agent required will be affected in a particular case by the amount of sulfur in the bath, the temperature of themolten iron, etc. I

Satisfactory alloys for the purpose of carrying out the present invention include the following:

Percent Percent Percent Percent Percent Percent; N 0. Mg Ni Ca Si Ce The foregoing alloys are satisfactory for the treatment of ordinary base gray cast irons and will provide satisfactory results in the usual case with additions of about 0.75% to about 1.25%, e.g., about 1%, by weight of the molten iron. These small additions insure high nickel economy in the use of the alloy. In special cases, such as the case (for example, in a pipe foundry) in which the temperature of the molten metal to be treated may be about 2450 F. (rather than the usual case in which the molten metal temperature is about 2700 to 2750 F.) or the case in which the sulfur content of the molten iron to be treated is very low, e.g., not exceeding about 0.01%, additions of the alloy on the order of about 0.25% or about 0.30% by weight of the molten iron may be employed. In such cases, even greater economy is achieved through the use of the present invention.

For the purpose of giving those skilled in the art a better appreciation of the advantages of the invention, the following illustrative example is given:

An addition of 0.8% by weight of an alloy containing 27.8% magnesium with the balance essentially nickel was plunged by means of an inverted refractory-covered cup into a ladle containing 1000 pounds of molten iron which had a sulfur content of about 0.035% and a nickel content of about /2%. The column of molten iron had a ratio of height to diameter of about 1.221 and the inverted cup was plunged through the molten iron to a distance of about 1% inches from the ladle bottom. Magnesium was retained in the iron in the amount of 0.059% and the final nickel content was 1.02%. The thus-treated iron was then inoculated with about 0.75% of ferrosilicon and cast into castings which had contained graphite in a spheroidal form.

These figures show a distinct advantage over an alloy containing about magnesium, with the balance essentially nickel. In the same operation, 0.95% of the 15% magnesium alloy was required for a retention of 0.057% magnesium and the residual nickel was 1.35%.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be Within the purview and scope of the invention and appended claims.

I claim:

1. In the method for introducing magnesium into molten cast iron, the improvement which comprises establishing a column of molten cast iron having a height at least substantially exceeding the thickness thereof and plunging substantially to the bottom of said column an addition agent containing about 25% to 35% magnesium, up to about 2% carbon, up to about 30% silicon, up to about 2% of a rare earth metal, up to about 5% calcium and the balance essentially nickel, and holding said agent substantially in position in said column until said agent is substantially melted, whereby an improved recovery in the molten iron of magnesium contained in said agent is obtained as compared to the magnesium recovery obtained from agents containing either greater or lesser amounts of magnesium.

2. In the method for introducing magnesium into molten cast iron, the improvement which comprises establishing a column of molten cast iron having a height at least one and one-half times greater than the diameter thereof, plunging substantially to the bottom of said column an addition alloy containing about 25 to 32% magnesium, up to about 2% carbon, up to about 30% silicon, up to about 2% of a rare earth metal, up to about 5% calcium and the balance essentially nickel, and holding said alloy substantially in position in said column until said alloy is I substantially melted, whereby an improved recovery in the molten iron of magnesium contained in said alloy is obtained as compared to the magnesium recovery obtained from alloys containing either greater or lesser amounts of magnesium.

3. In the method for introducing magnesium into molten cast iron, the improvement which comprises establishing a column of molten cast iron having a height at least twice as great as the diameter thereof, plunging substantially to the bottom of said column an addition alloy containing about 25% to 32% magnesium, up to about 2% carbon, up to about 30% silicon, up to about 2% of a rare earth metal, up to about 5% calcium and the balance essentially nickel, and holding said alloy substantially in position in said column until said alloy is substantially melted, whereby an improved recovery in the molten iron of magnesium contained in said alloy is obtained as compared to the magnesium recovery obtained from alloys containing either greater or lesser amounts of magnesium.

Millis et al. Oct. 25, 1949 Millis et al. Oct. 25, 1949 

1. IN THE METHOD FOR INTRODUCING MAGNESIUM INTO MOLTENJ CAST IRON, THE IMPROVEMENT WHICH COMPRISES ESTABLISHING A COLUMN OF MOLTEN CAST IRON HAVING A HEIGHT AT LEAST SUBSTANTIALLY EXCEEDING THE THICKNESS THEREOF AND PLUNGING SUBSTANIALLY TO THE BOTTOM OF SAID COLUMN AN ADDITION AGENT CONTAING ABOUT 2K% TO 35% MGNESIUM, UP TO ABOUT 2% CARBON, UP TO ABOUT 30% SILICON, UP TO ABOUT 2% OF A RATE EARTH METAL, UP TO ABOUAT 5% CALCIUM AND THE BALANCE ESSENTIALLY NICKEL, AND HOLDING SAID AGENT SUBSTANIALLY IN POSITION IN SAID COLUMN UNTIL SAID AGENT IS SUBSTANTIALLY MELTED, WHEREBY AN IMPROVED RECOVERY IN THE MOLTEN IRON OF MAGNESIUM CONTAINED IN SAID AGENT IS OBTAINED AS COMPARED TO THE MAGNESIUM RECOVERY OB- 